> I'm specifically looking for some kind of dimensions on the spiral
> casing. If anyone has more info let me know

I suggest you envision a spiral wrapped around the axel 5-10 times,
narrowing in crossection as it spirals out. The outer casing needs to
wrap around at this spiral angle until it laps itself and makes a rather
narrow slot. The slot is the exit nozzle entrance. The nozzle, which can
be wrapped around the pump or straight, needs to expand gradually, about
one unit in seven as I recall, so the gas remains in intimate contact
with the wall as it expands. This will result in the highest pressure.
If you plug the output, the flow will stall, and the pressure will drop.
I think this will result in pulsations. This kind of pump needs a steady
flow, since the nozzle is key to determining the peak operating
pressure.

Drew Marinich

I m not following your explanation. If you could draw me a picture that would be the most helpful. Thank s for writting Cheer s Andy ... I suggest you envision

Message 4 of 7
, Sep 8, 2005

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I'm not following your explanation. If you could draw me a picture that would be the most helpful. Thank's for writting

I suggest you envision a spiral wrapped around the axel 5-10 times,narrowing in crossection as it spirals out. The outer casing needs towrap around at this spiral angle until it laps itself and makes a rathernarrow slot. The slot is the exit nozzle entrance. The nozzle, which canbe wrapped around the pump or straight, needs to expand gradually, aboutone unit in seven as I recall, so the gas remains in intimate contactwith the wall as it expands. This will result in the highest pressure.If you plug the output, the flow will stall, and the pressure will drop.I think this will result in pulsations. This kind of pump
needs a steadyflow, since the nozzle is key to determining the peak operatingpressure.

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I'm not following your explanation. If you could draw me a picture that
would be the most helpful.

Draw a
spiral (I am bad at this so I will do it verbally if you don't
mind).

Now redraw it with each loop slightly narrower than the one before.
Make around 10 loops to fit into your TT.

Put a
pencil down at the outer edge where you will exit the turbine inner cavity,
and trace back along the spiral till you have come around 360 degrees and
the pencil down point is just out along the radius from where you are.
The line you just drew is the outer case. The turbine fits inside this last
point as close as you can fit it without scraping.

Now
you have a narrow slot where the exiting gas is moving quite fast, only
a bit slower than the outer edge of the turbine blades. But the pressure is
low. We need to expand the gas slowly, say every seven mm the nozzle gets one mm
wider. As the gas slows and the crossection expands, the pressure increases.
Where the gas pulls away from the side wall due to back pressure you have
reached the maximum pressure you can attain. This is right for subsonic
flow, I am pretty sure. For super sonic flow, things are more
complicated.

Drew Marinich

Are you a engineer at boeing? Do you have access to CAD program? I use Pro E. I plan on modeling everything before I build it. If you could take a look when

Message 6 of 7
, Sep 8, 2005

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Are you a engineer at boeing? Do you have access to CAD program? I use Pro E. I plan on modeling everything before I build it. If you could take a look when I'm done that's the only way I could be sure I'm following what your talking about. "McGalliard, Frederick B" <frederick.b.mcgalliard@...> wrote:

I'm not following your explanation. If you could draw me a picture that would be the most helpful.

Draw a spiral (I am bad at this so I will do it verbally if you don't mind).

Now redraw it with each loop slightly narrower than the one before. Make around 10 loops to fit into your TT.

Put a pencil down at the outer edge where you will exit the turbine inner cavity, and trace back along the spiral till you have come around 360 degrees and the pencil down point is just out along the radius from where you are. The line you just drew is the outer case. The turbine fits inside this last point as close as you can fit it without scraping.

Now you have a narrow slot where the exiting gas is moving quite fast, only a bit slower than the outer edge of the turbine blades. But the pressure is low. We need to expand the gas slowly, say every seven mm the nozzle gets one mm wider. As the gas slows and the crossection expands, the pressure increases. Where the gas pulls away from the side wall due to back pressure you have reached the maximum pressure you can attain. This is right for subsonic flow, I am pretty sure. For super sonic flow, things are more complicated.

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